• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.1
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• pp.74-80
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• 2007

This paper proposes the novel open-fault detection/isolation scheme of inverter switch in two-phase excited VSI. This scheme identify open-fault using voltage sensor at lower switches of each phase according to the operating mode. It has benefit of simple implementation, fast detection and robustness in the load so that stab of the system is improved. Also, at faulty mode, it minimizes faulty effect and makes possible continuous operation through the reconfiguration procedure applying four-switch operation. The validity of proposed fault detection scheme is verified by experimental results.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.491-492
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• 2016

This paper presents a robust feedback control design to mitigate the effect of grid voltage disturbances for three-phase grid-connected inverters in distributed generation systems. The proposed strategy consists of two major design steps. First, the controller is synthesized using the internal model principle to achieve a good reference tracking and disturbance rejection performance. Then, the feedback gain is systematically obtained by solving the linear matrix inequality conditions which are directly derived from the stability criteria. The main contribution of this paper is that the complexity of control structure can be substantially reduced and transient response is improved as compared with the existing robust control design methods. The simulation results are given to prove the validity of the proposed control scheme.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.127-132
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• 2000

This paper describes a 3-phase Line-Interactive APF system and analyzes its operating characteristics considering LC Filter output characteristics. Topology of APF is similar to that of Off-Line UPS in the point of parallelly operating inverter system. So it is possible to be multi-functioned active compensating system according to power condition. Likewise this actively operating system from APF to UPS and vice versa is often to be called Line-Interactive system. And more than that Line-Interactive system needs precise design of LC filter on converter output side to make this system fully operate in both APF and UPS modes. The problem in this point is how to design LC Filter to be contented with two different system characteristics so this paper analyzes this problem and proposes its design procedures. Then suggested filter design is verified to be contented by the simulations and experimental results

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1352-1364
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• 2013

This paper describes a novel structure for single phase Unified Power Quality Conditioner-Distributed Generation (UPQC-DG) with direct grid connected DC-AC converter for low DC output DG systems which can be used not only for compensation of power quality problems but also for supplying of load power partly. This converter has been composed of one full-bridge inverter, one three winding high frequency transformer with galvanic isolation and two cycloconverters. Proper control based on Input Output feedback Linearization is used to tracking the reference signals. The simulation and experimental results are presented to confirm the validity of the proposed approach.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.4
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• pp.61-72
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• 2007

This study proposed a high efficiency DC-DC converter with a new current doubler rectifier for fuel-cell systems for use with the Nexa(310-0027) PEMFC from the Ballard Co. The proposed high efficiency DC-DC converter for the fuel-cell system generated ZVS by applying partial resonance and using a phase shift PWM control method. Constantly switching frequency, loss of switching, peak current, and peak voltage were reduced by this system. In addition to this system, two inductors were attached to a rectifier circuit allowing it to be able to provide the direct current(DC) and DC voltage safely to a load with reduced ripple components. Also, by using the newly proposed current doubler rectifier, the high frequency DC-DC converter for the fuel cell system was capable of reaching a highest efficiency of 92[%] as compared to 88.3[%] efficiency in previous results, which means that efficiency increased 3.7[%]. The overall results were confirmed by a simulation and laboratory experiment.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.210-211
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• 2016

션트 저항을 이용하여 3상 인버터의 전류를 측정하는 방법은 가격 경쟁력이 우수하여 다양한 산업 분야에서 응용되고 있다. 본 논문에서는 시스템의 원가를 절감하기 위해 2개의 레그-션트 저항을 이용하여 3상 인버터의 상 전류를 측정하는 방법을 제안하고 측정이 가능한 영역에 대하여 분석한다. 2개의 레그-션트 저항을 이용할 경우 기존 3개의 레그-션트 저항을 이용했을 때보다 시스템의 가격이 감소할 뿐만 아니라 레그-션트 저항에서 발생하는 손실이 감소하여 전체 인버터의 효율이 증가한다는 장점이 있다.

• Journal of Power Electronics
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• v.16 no.2
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• pp.675-684
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• 2016

This paper presents a new stand-alone wind-based induction generator system with constant frequency and adjustable output voltage. The proposed generator consists of a six-phase cage-rotor induction machine with two separate three-phase balanced stator windings and a three-phase space vector pulse width modulation inverter that operates as a static synchronous compensator (STATCOM). The first stator winding is fed by the STATCOM and used to excite the machine while the second stator winding is connected to the generator external load. The main frequency of the STATCOM is determined to be constant and equal to the load-requested frequency. The generator output frequency is independent of the load power demand and its prime mover speed because the frequency of the induced emf in the second stator winding is the same as this constant frequency. A sliding mode control (SMC) is developed to regulate the generator output voltage. A second SMC is used to force the zero active power exchanged between the machine and the STATCOM. Some simulation and experimental results are presented to prove the validity and effectiveness of the proposed generator system.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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• pp.176-183
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• 2014

Three-phase four-wire distribution systems are used for both three-phase three-wire loads and single-phase two-wire consumer appliances in South Korea, Myanmar and other countries. Unbalanced load conditions frequently occur in these distribution systems. These unbalanced load conditions cause unbalanced voltages for three-phase and single-phase loads, and increase the loss in the distribution transformer. In this paper, we propose constant DC capacitor voltage control based strategy for the active load balancer (ALB) in the three-phase four-wire distribution systems. Constant DC capacitor voltage control is always used in active power line conditioners. The proposed control strategy does not require any computation blocks of the active and reactive currents on the distribution systems. Balanced source-side currents with a unity power factor are obtained without any calculation block of the unbalanced active and reactive components on the load side. The basic principle of the constant DC capacitor voltage control based strategy for the ALB is discussed in detail and then confirmed by both digital computer simulations using PSIM software and prototype experimental model. Simulation and experimental results demonstrate that the proposed control strategy for the ALB can balance the source currents with a unity power factor in the three-phase four-wire distribution systems.

• Journal of the Korean Solar Energy Society
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• v.37 no.6
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• pp.1-12
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• 2017

The DC link of Grid-Connected 3-Phase 3-Level T-type Photovoltaic PCS (PV-PCS) consists of two series connected capacitors for using their neutral voltage. The mismatch between two capacitor characteristics and transient states happened in load change cause the imbalance of neutral voltage. As a result, PV-PCS performance is degraded and the system becomes unstable. In this paper, a mathematical model for analyzing the imbalance of neutral voltage is derived and a compensation method using offset voltage is proposed, where offset voltage adjusts the applying time of P-type and N-type small vectors. The validity of the proposed methods is verified by simulation and experiment.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.8
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• pp.1153-1158
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• 2010

In this paper, We make horizontal balancer (HB) and confirm a possibility of the technique that can be applied to ship through horizontal vibration reduction experiment. We use MATLAB as the simulator tool and experimental equipment consists of two induction motors shafts of which cam type unbalanced loads are fixed to, DSP and inverter circuit. Two induction motors perform roles as vibrator and balancer respectively, DSP control softwares such as speed, phase and vector control program. The simulation and experimental results show that the balancer characterizes good vibration reduction by phase control.